Normally lead-acid storage batteries use concentrated sulfuric acid diluted by distilled water as electrolyte. During the production of lead-acid storage batteries, due to the difficulties of treating acidic electrolyte, serious environment pollution is unavoidable in assembling, application and disuse. In addition to the releasing of acidic smog during the utilization of conventional open-mouth type lead-acid storage batteries, it corrodes the junction parts of the batteries and is not safe for application and transportation.
Recently, a gel electrolyte has been developed in the form of a high-capacity gel electrolyte described in patent ZL90102355. This gel electrolyte contains silica gel and sulfuric acid, the main component of the silica gel is SiO2 x H2O, wherein the weight ratio of sulfuric acid and SiO2 is 4.5/10.5. Although the batteries using such gel electrolyte show high capacity and have advantages compared to the batteries using sulfuric acid electrolyte, this type gel electrolyte is still using a large amount of sulfuric acid, and it also has the disadvantages such as environment pollution, unsafe transportation and application.
In addition, the capacity of the batteries using gel-type electrolyte is 70% or even less of the capacity of the batteries using sulfuric acid electrolyte. Therefore, the specific energy density is relative low and internal resistance is high. It also looses water more easily then becomes increasingly harder, which decrease the performance and cycle life of the batteries.
Before this invention, the inventor has previously proposed a complex silicate electrolyte without sodium (PCT/CN99/00116). This silicate electrolyte is composed of an organic silicane and sulfuric acid at certain weight ratio. It overcomes the main disadvantages of sulfuric acid electrolyte. However, it was found that due to using sodium silicate as gel, the filling of gel into the batteries is difficult. Sometimes the filling of the electrolyte needs to be repeated several times. Thus, the filling processes become complicated. Such electrolyte cannot avoid the presence of sodium, once the concentration of the sodium in the silicate electrolyte exceeds 0.1%, the viscosity of the electrolyte is increased significantly and becomes mushy. The electrolyte tends to lost water during application and leads to harden and crack. It decreases the performance of the batteries obviously and leads to poor self-discharge and high internal resistance and short cycle life.